Electrode structure of electrolytic condensers



March 6, 1934. J. E. LILIENFELD ELECTRODE STRUCTURE OF ELECTROLYTICCONDENSERS Filed Oct. 31, 1931 INVENTOR duuusEo GARL m lE/VFEL 0ATTGRNEY Patented Mar. 6 1934 UNITED {STATES rescue ELECTRODE STRUCTUREOF ELECTRGF LYTIC CONDENSERS Julius Edgar Lilieni'eld, Winchester, Mass,as= signor to Ergon Research Laboratories, liner, Malden, Mesa, acorporation of Delaware Application October til, 193i, Serial No.572,292 10 claims, (or camera The invention relates to electrolyticcondensers, and more particularly to a novel construction and operationthereof. The invention is particularly adaptable to electrolyticcondensers of the A. C.

'6 type and utilizing a single container for the elec= trolyte, saidcontainer with electrolyte then constituting the cathodic electrode andretaining two systems of filmed electrodes of alternately dis posedelements of opposite polarity, which are it) mounted therein forconnection to a source of alternating current.

In. arrangements of this type, the difirent ele= ments constituting thefilmed electrodes are lo cated with their surfaces lying closelytogether ld'so that the capacity current goes through the electrolytedirectly from one layer tothe next. However, certain portions, moreespecially the supporting riser members or rods for the elsetrodes,present outer surfaces which face the fun 29 side wall of the container.This creates a condition whereby the capacity current going to theoutside surface of each layer of the electrodes travels from. thenon-formed inside wall of the cathodic container to the formed outsidesurime 26 of the riser or rod.

It is particularly desirable, especially for counmercial reasons, toconstruct these containers oi aluminum, and it has been observed thatthe here= inbefore described condition results in the disin so tegrationof the aluminum metal surface facing the risers such that relativelylarge particles of aluminum are loosened from the container wall, dropor are torn off, and collect on the bottom. This destructive action willeventually perforate 8d the wall of the container, and it is an objectof the present invention to make provision for pre= venting suchdestructive action thereon.

This may readily be effected by introducing in termediate and activeelectrode members of suit- 4o ablemetal between such parts of theelements of the two systems of filmed electrodes as do not face eachother across the narrow spacing, but rather .face the container. Forexample, copper strips may be secured to the supporting structure in tosuch a manner as to partly surround the risers or supporting rods forthe electrodes, the same being located between such risers and thecontai'ner wall and in close proximity to the former.

In the provision of these metallic active elec- 50 trodes, I have found,furthermore, that not only is the deterioration of the container wallobviated, but an important effect may'be had upon the electrolyteitself. I have discovered that the electrolyte utilized for electrolyticcondensers may be 55 constituted as entirely free of any alkalinecomponents, such as result from the usual addition of borer; or likealkali salts to electrolytes of this nature. Thus, it is possible to usea nearly satu= rated'solution of boric acid, salicylic acid, etc, inwater, if the same be also saturated with electroco positive ions suchas may be obtained from metals as copper, nickel, chromium, cadmium,cobalt, zinc, etc. Or, alcoholic solutions of such weal: acids, as wellas a mixture of water and alcohols, may he utilized and saturated withmetallic ions. 'lnese ions may readily be introduced into theelectrolyte, for example, by immersing two of the metal electrodestherein and causing a current flow therebetween until the electrolytebecomes saturated with the electropositive ions. Such yo saturation hasthe piupose merely of reducing the high resistance of electrolytes ofthis nature, and in the case of a pure aqueous boric acid solutionutilized for the electrolyte, copper ions have been found veryefiective. this connection it is desirable to have some active coppersurfaces permanently located in the novel electrolyte for maintainingits satura= tion with copper ions and the provision of the intermediateactive electrodes in the condenser construction hereinbefore describedserves also for the purpose of maintaining this ion concen= tration. I

Other metal ions such as nickel, chromium, cadmium, cobalt, zinc, etc,may be utilized, but copper ions from the intermediate active elec trodeafiord a relatively inexpensive and highly satisiactory means forattaining the desired re= suits.

in the use of an extremely high resistance elec trolyte for anelectrolytic condenser, it becomes necessary to space the electrodeelements rela tively closely; and by utilizing an electrolytesubstantially free from alkaline components, there is a relatively lowelectric leak therebetween, the condenser possesses a higher breakdownvoltage, requires a lower biasing voltage, and the power loss in thedielectric layer is particularly low. A further reduction in power lossresults through the addition of the metallic (copperl ions inasmuch asthe resistance of the electrolyte is thereby appreciably diminished. Thesaid electric layer, furthermore, is more stable in that too it retainsits organized condition better during the idling periods, thus reducingthe electric leak after such periods.

The accompanying drawlngillustrates one sin-=- bodiment of anelectrolytic A. C. condenser to which the novel provisions aforesaid are"particularly applicable, and in the drawing Fig, i no is a verticalsection through an A. C. condenser provided with intermediate activeelectrodes; and Fig. 2 is a horizontal section thereof, taken on theline 22, Fig. 1.

Fig. 3 is a front elevation, and Fig. 4 an underheath view of an activeintermediate electrode as utilized in the novel combination.

Referring to thedrawing, designates a container which is of aluminum andis designed to retain a suitable electrolyte l1 and the novel electrodestructure. The electrolyte is, preferably; free from alkalinecomponents, for example, it may consist of an aqueous, solution of boricacid or of salicylic acid, or of alcoholic solutions thereof. To reducethe resistance of said electrolyte, the same is saturated withelectropositive (metallic) ions, for example, those of copper as intemporarily passing an electric current between two copper electrodes(not shown) dipping therein and as is well understood, or by addingthereto a suitable salt such as copper borate.

' Into the electrolyte is designed to dip, for example in the case ofalternating current operation, a plurality of systems of electrodescomprising the respective formed aluminum plates 12 and 13 of oppositepolarity andshown in the present instance of frusto-conical shapesubstantially as set forth in my copending application Serial No.531,901. These plates may be mounted, similarly to the arrangement shownin the aforesaid application, upon two sets of risers l5 and 16 whichare equidist'antly spaced around the vertical axis of the respectiveelectrode eleinents. @ne of each set of risers, also, has an upperportion 17 and 18, respectively, projecting beyond the cover member 19of the condenser and affording the terminal leads 20 and 21, by whichconnection may be had to a suitable source of alternating current, theelectrolyte of the condenser being biased to a predetermined negativevoltage, for example, as is set forth in my copending application SerialNo. 462,252. Provision is also made for mounting above and below the twosets of filmed elements top and bottom shielding elements 22 and 23 ofcopper, as on risers 24 which are thus electrically connected to thesaid coyer member through the said risers 24.

The two sets of risers 15 and 16 are arranged to be supported at thebottom ends by the bottom plate 26 and are insulated therefrom by therespective recessed insulating bushings 2'7 and 28, respectively,substantially in the manner set forth in my said application, Serial No.531.901, and the same also pass through an upper plate 29 carried by therisers 24.

In accordance with the invention, the exposed outer surfaces of therisers 15 and 16, which constitute active electrode surfaces not facingone of opposite polarity across a narrow spacing, but rather the innerwall of the container 10, are arranged to be surrounded over the saidexposed portions by further metallic electrodes located in proximity tosaid surfaces and intermediate the same and the inner wall of thecontainer. For example, thin strips 30 of a metal such as copper,nickel, chromium, cadmium, cobalt, zinc, etc., and preferably thefirst-named, are rigidly secured at their opposite ends through endflanges 31 and 32 to the said bottom and top plates 26 and 29.

In the provision of these active intermediate electrodes the capacitycurrent may go directly from the strips tothe risers and not from thenon-formed inside wall of the container to the formed outer surface of ariser. Disintegration of the inner wall of the container is thusobviated, and the life of the condenser greatly prolonged.

Also, the benefits resulting from the use of narrowly spaced electrodesand a relatively high resistance electrolyte may thus be retained.Furthermore, these metallic shielding or active intermediate electrodemembers serve to maintain the concentration of metallic ions in theelectrolyte and, of course, should be of the same metal as the ionscontained in the electrolyte.

I claim:

1. The combination with an A. C. electrolytic condenser embodying acathodic metallic container for electrolyte and coacting electrodesmounted therein, and comprising a plurality of formed elements narrowlyspaced apart; of shielding cathodic electrodes of non-filming metalinsulated from the formed elements and located between the inner wall ofthe container and such parts of the electrode elements as are unexposedto a coacting element.

2. The combination with an A. C. electrolytic condenser embodying acathodic aluminum container for electrolyte and coacting electrodesmounted therein, and comprising a plurality of formed elements narrowlyspaced apart; of shielding cathodic electrodes of non-filming metalinsulated from the formed elements and located between the inner wall ofthe container and such parts of the electrode elements as are unexposedto a coacting element.

3. The combination with an A. C. electrolytic condenser embodying acathodic metallic container for electrolyte and coacting electrodesmounted therein, and comprising a plurality 0! formed elements narrowlyspaced apart; of shielding cathodic electrodes of copper insulated fromthe formed elements and located between the inner wall of the containerand such parts of the electrode elements as are unexposed to a coactingelement.

4. The combination with an A. C. electrolytic condenser embodying acathodic metallic container for electrolyte and coacting electrodesmounted therein and constituted by alternately disposed formed platesnarrowly spaced apart, and supporting risers for interconnectingalternate plates; of shielding cathodic electrodes of non-filming metalinsulated from the formed plates and located between the inner wall ofthe container and the outer surfaces of said risers which are unexposedto a coacting element.

5. The combination with an o. electrolytic condenser embodying acathodic metallic container for electrolyte and coacting electrodesconstituted by alternately disposed formed plates, supporting risers forinterconnecting alternate plates, and top and bottom cathodic platesassociated with the risers and insulated therefrom; of metal stripssecured at their opposite ends to the respective plates and about thesurface of the risers facing the inner wall of the'container andnarrowly spaced from said risers.

6. The combination with an A. C. electrolytic condenser embodying acathodic metallic container for electrolyte and coacting electrodesconstituted by alternately disposed formed plates, supporting risers forinterconnecting alternate plates, and top and bottom cathodic platesassociated with the risers and insulated therefrom; of strips of copperhaving top and bottom flanges rigidly secured at their opposite ends tothe respective plates and extending about the surface of the risersfacing the inner wall of the container and narrowly spaced from saidrisers.

7. An A. C. electrolytic condenser, comprising a cathodic metalliccontainer for an electrolyte, an electrolyte embodying a free weak acidof the group consisting of boric acid, salicylic acid and alcoholicsolutions thereof and free from alkaline components, said electrolytecontaining also electropositive ions other than alkaline ions, aplurality of filmed electrodes dipping into said electrolyte, andnon-filming cathodic metal elements associated with said filmedelectrodes for shielding the container and for maintaining theconcentration of the electropositive ions of said electrolyte.

8. An A. C. electrolytic condenser, comprising a cathodic metalcontainer for an electrolyte, an electrolyte embodying a free weak acidof the group consisting of boric acid, salicylic acid and alcoholicsolutions thereof free from alkaline components, said electrolyte alsocontaining copper ions, a plurality of filmed electrodes dipping intosaid electrolyte, and means associated with the said filmed electrodesfor shielding the container and for maintaining the concentration of thecopper ions in the electrolyte.

9. An A. C. electrolytic condenser, comprising a cathodic metalcontainer for an electrolyte, an electrolyte embodying a free weak acidof the group consisting of boric acid, salicylic acid and alcoholicsolutions thereof free from alkaline components, said electrolyte alsocontaining copper ions, a plurality of filmed electrodes dipping intosaid electrolyte, and strips of copper dipping into the electrolyte formaintaining the concentration of the copper ions therein and locatedbetween the inner wall of the container and such parts of the filmedelectrodes as are unexposed to a coacting electrode.

10. The combination with an A. C. electrolytic condenser, embodying acathodic aluminum container for an electrolyte, an electrolyte of thegroup consisting of boric acid, salicylic acid and alcoholic solutionsfree from alkaline components, said electrolyte containing also copperions, and coacting electrodes mounted therein and comprising a pluralityof formed elements narrowly spaced apart; of strips of copper locatedbetween the inner wall of the container and such parts of the electrodeelements as are unexposed to a coasting element, the said stripsconstituting shielding cathodic electrodes and serving also to maintainthe concentration of the copper ions in the electrolyte.

JULIUS EDGAR LILIENFELD.

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